Welcome.
I'm using one of the online charts, which are know to be wrong.
A D40 with an AJ prefix is listed for 1965-1969. According to the chart, your serial number is after the last one made in 1969. That is not unusual. Guild changed the numbering scheme circa 1970 but they did not do so retroactively. So I would be comfortable in saying it was finished in 1970.
As to where, it was probably made in Westerly, Rhode Island. Operations were being moved from Hoboken, NJ circa 1965-1970 but almost everything was being built in Westerly by 1970. Note, however, that Guild put "made in Hoboken' labels on instruments made in Westerly, at least until they used up the stock of the former.
This is mostly from memory so expect corrections, but at least the discussion got started